furrr 0.1.0

Features:

future_pmap_*() functions have been added to mirror pmap().

The future.* arguments to each function have been replaced with an overarching .options argument. Use future_options() to create a set of options suitable to be passed to .options. This change streamlines the interface greatly, and simplifies documentation (#8, @hadley).

future_invoke_map_*() functions have been added to mirror invoke_map().

More documentation and examples have been added.

Added the ability to use a progress bar with .progress = TRUE for multicore, multiprocess, and multisession plan()s.